Controller for display board



Jan- 10, 1967 T. R.B| AKEs| EE ETAL 3,297,927

CONTROLLER FOR DISPLAY BOARD 4 Sheets-Sheet l Filed Feb. 20, 1964 mbu Qu@ Q INVENTORS 7710,14/15 A. BLA/(51.55,

REA/MAM R41/z, A//QUETTE BY THE/.Q ,47702/1/53/6 HA/Qe/s, /f/ECH, Rasse/L #een O llllll .WNUDFUDMQ @ll N NxQk. Q:

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Jam 10, 1967 T. Rt BLAKE-.SL55 ETAL 3,297,927

CONTROLLER FOR DISPLAY BOARD Filed Feb. 20, 1964 4 Sheets-Sheet 2 MESSAGE FORMAT F/RST B/T /Tz an' 3 517'4 B17' 5 B/T 6 RECEIVED f Y F J r i l l t b/'f of #E/RST LETTER---V /005 1 l l l I 1gb/'f 0f CHARACTER 21 SECO/VD LETTER- /OS CHARACTER l R15-AMAN RAUL N/QUETTE BY THE/R ATTORNEYS HABE/s, K/ECH, RUSSE/ L KERN Jan. 10, 1967 T. R. BLAKESLEE ETAL 3,297,927

CONTROLLER FOR DISPLAY BOARD 4 Sheets-Sheet 5 Filed Feb. 20, 1964 Jam-10,1967 T. ROBLAKESLEE ETAI. `3,297,927

CONTROLLER FOR DISPLAY BOARD Filed Feb. 2o, 1964 4 Sheets-sheet 4 T/ME ELECTRONIC POWER Sw/rcH/Na oPERAT/o/ 5/ T l COUNTER C HAR/1C TER 5 TRANS/nom coun TER -72 x -D/SP/.AY Mapu/.E L3 47H SELECT/0^ CHARACTER 7/ -Tz ll- SEL/5cm? FNA/ HOM/N6 .l X5

REED L IT RELAY v HoR/z. L/FTER opERAT/NG PowER 0N Q T -T i 6 STEPS -T3 (E/T *2) Tl X6 i -TZ MODULE RELAY i POWER 0^/ l 77 4 STEPS T2 (E/T #3) -g T 'zl X 7 -Tz MoToR -T POWER 0N i L/FTER RELEAS/A/ TIM/NG D/A GRAM INVENToRs M6 6 7710/14/15 BLAKESLEE,

REA/WAN @4u/ A /mL/ETTE BY THE/,Q ATTORNEYS HARR/S, f/ECH, RUSSE/1 KERN United States Patent O 3,297,927 CONTROLLER FOR DISPLAY BOARD Thomas R. Blakeslee, Sherman Oaks, and Reaman Paul Niquette, Palos Verdes Estates, Calif., assignors to Scantlin Electronics, Inc., Los Angeles, Calif., a corporation of Delaware Filed Feb. 20, 1964, Ser. No. 346,229 7 Claims. (Cl. S18-138) This invention relates to stepping motors and the like and to control circuitry for operating stepping motors. The invention will be described herein as used in driving the stepping motors of a security price display board such as is described in the Icopending application of Howard W. Beckwith entitled Display Board, Serial No. 219,260, led August 24, 1962, and assigned to the same assignee as is the present application.

A display board [provides for the visual display of a large number of symbols, ordinarily price data, and for rapid change of symbols in response to input information. In the embodiment to be described herein, the symbols in the form of figures are carried on a pair .of concentric cylinders, providing for six symbol-s equally spaced about the inner cylinder and live symbols and a gap equally spaced about the outer cylinder. The symbols of the inner cylinder are viewed through the gap in the outer cylinder. The cylinders are viewed through a mask so that only a single symbol is displayed. The display board includes means for rotating the inner cylinder through at least 300 to position each of the symbols at the gap in the outer cylinder yand means for rotating the outer cylinder through at least 300 to position-each of the symbols on the outer cylinder at at the mask location for viewing. Such cylinder rotation may be accomplished by an electric stepping motor with the motor rotating in one direction for driving the inner cylinder and rotating in the opp-osite direction for driving the outer cylinder. Such an arrangement is shown in the aforementioned copending application. The present application describes a controller for operating the stepping motor in response to security price data received from a security exchange, a data handling system, a computer memory or other source.

The incoming security price data will be in binary code form land the invention contemplates a shift register or counter actuated by the incoming binary code with register stages corresponding to motor drive coils and with register stepping producing corresponding mechanical motion of the stepping motor resulting in a direct one to one relation between lregister operation and motor operation.

It is an object of the invention to provide a controller for a stepping motor having a plurality of drive coils positioning a rotating member as a function of the excitation of the coils with the controller driving the rotating member in a selected direction to a selected position and including a multistage reversible shift register with the output inverted to the input and having a stage corresponding to each drive coil, means for selectively shifting said register a predetermined number of counts clockwise and counterclockwise in response -to an input code, a power switching unit for each drive coil with means for selectively energizing the drive coil in opposing polarities from a power source, and circuit means :for coupling the output of a shift register stage to a corresponding power switching unit in controlling relation for energizing a drive coil asa function of the correspond-ing register stage condition.

It is a further object of the invention to provide such a controller for a stepping motor having n drive coils for 3,297,927 Patented Jan. 1 0, 1967 positioning the rotating member to any of 411 positions and including an n stage reversible shift register and intermediate` switching means coupled to each of the power switching unlts in controlling relation for de-energizing a drive coil at a time intermediate the shifting times of the register.

It is a further object of the invention to provide such a controller including means for generating clockwise and counterclockwise shifting pulses for the register and means for selectively coupling lthe clockwise and counterclockw1se pulses to the register as a function of the first bit of the'input code for determining the direction of shift of the reglster, and means for controlling the number of shifting pulses coupled to the register as a function of the succeeding bits of the input code for shifting the register in a predetermined direction to a predetermined condition. An additional object is to provide such a controller including a timing pulse train source and gate means for coupling the pulse train source -to the means for generating shifting pulses for periods determined by each of the succeeding bits of the input code for shifting theregister in the predetermined direction to the predetermined condition.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which Will more fully appear in the course of the following description. The drawings merely show and the description merely describes a preferred embodiment of the present invention which is given by way of illustration or example.

In the drawings:

FIG. 1 diagrammatically illustrates the operation of a display board incorporating the controller of the invention;

FIG. 2 is a schematic diagram of a module switching relay for energizing a stepping motor;

FIG. 3 diagrammatically illustrates the operation of the shift register and stepping motor;

FIG. 4 is a block diagram illustrating the controller of the invention;

FIG. 5 is a diagram illus-trating the form of the bina-ry coded input message; and

FIG. 6 is a timing diagram for the controller.

The display board in which the controller of the invention is utilized includes a plurality of identical display modules. Each module provides for the display of twenty numbers in tive horizontal rows of four digit numbers. The numbers are on cylinders which have a ver-tical shaft through each column of ve with a stepping motor at the top of each vertical shaft. A solenoid operated horizontal lifter allows the number cylinders in the desired horizontal row to dr-op down and engage the vertical shafts. In this way, although the stepping motors turn the vertical shafts for every number setting, only the desired horizontal rows will be engaged and therefore set.

The numbers are painted on two concentric cylinders with even numbers on the outer -cyl-inder and odd numbers on the inner cylinder. The outer cylinder engages the shaft only if the shaft turns in the clockwise direction and the inner cylinder engages only when the shaft turns in the counterclockwise direction. Sixty degrees of arc can be allocated to each of the ten numbers for viewing with the six motor positions.

The stepping motor itself may consist of three pairs of coils grouped around a cylindrical 'magnet which is molded into the top of the vertical shaft. The three pairs of coils have a common return so that only three input signal wines yare required for each stepping motor. Shaft position is determined by the polarity of voltages applied to the three input wires.

A schemati-c diagram of .a typical stepping motor is shownv in the lower right portion of FIG. 4 and includes coils 10, 11, 12. Terminals 13, 14, 15 serve as input terminals for the respective coils. The other terminal of each coil is connected to circuit ground through the normally open contacts of a relay 16. The coil inputs are identified as M1, M2 and M3, respectively, for reference purposes throughout this specification. The symbol M1+ indicates that a positive polarity voltage is applied to the M1 coil input terminal. Similarly the symbol M1- indicates that a negative polarity voltage is applied to the terminal.

The input voltages and magnetic polarities for each motor position are shown in FIG. 3 wherein the circular figure 17 represents the rotating magnet Icarried at the top of thevertical shaft. The small circles disposed around the large circle 17 correspond to the terminals of the motor in FIG. 4, with the letters N and S within the circles indicating the relative polarities of the terminals with respect to each other. v

All numbers or motor positions are set by sequencing or stepping, one position at a time, around the d-iagram until the desired number is reached. The motor always starts with the rotating member in the home position at the top center of FIG. 3. In this position, the vertical shaft is physically positioned between the engagement pins on the inner and outer cylinders so that it will engage one or the other, depending upon the initial direction of rotation. As the `motor steps, the proper cylinder is turned, against tension of a spring inside the cylinder, to a position past the number position actually desired. The horizontal lifter may then be released to disengage the cylinder from the shaft and the cylinder is moved in the opposite direction by the spring action to the lactual number position where it engages a detent arm of the released horizontal `lifter which maintains the cylinder in the set position. It should be noted that the stepping motor itself is not moved in the opposite direction by the spring action and this operation of the cylinder and horizontal lifter is not concerned with the stepping motor drive. When the cylinder is set in the desired position by the detent action, the vertical shaft and stepping motor are free to be returned to the home position to await the next input signal.

The construction and operation of the display module is described in detail in the aforementioned copending application. The electrical circuitry for a module is shown in FIG. 2. Four stepping motors 21, 22, 23, 24 of the type shown in FIG. 4 provide for driving the four vertical shafts. Five electromagnets 25, 26, 27, 28, 29 provide for actuating the horizontal lifters or row selector levers. The relay 16 utilizes seventeen sets of conta-cts -for connecting the motor coils and electromagnets to circuit vground when the particular module carrying the relay is to be actuated. With the relay 16 unenergized, application of signals to any of the leads V1-V4, H1-H5 produces no operation in the particular module. With the relay energized and the module in the active condition, application of signals to one or more motor coils and to one or more lifter magnets produces the cylinder rotation previously described.

The electrical control system for a complete display board -is shown diagrammatically in FIG. 1. The information to be displayed is fed from a data source 31 through a buffer 32 which provides temporary storage facilities, to a module selector 33 and a sequence controller 34. The incoming information will have a module` identification portion, a symbol identification portion and a symbol value. For example, when used for displaying stock prices, the incoming information will include the identification of the stock, identification of the data such as a new high, `a new low or last price, and the price itself. A typical message format is shown in FIG. 5. The module selector 33 has a plurality of output lines M1-Mn for energizing the relay 16 of each of the modules. The

module selector applies a relay actuating voltage to the particular output -line connected to the module which displays the price data for the particular stock on which information has just been received. This lmodule will be switched to the active condition and maintained thus until the change operation is complete.

The sequence controller 34 has five output lines H1-H5 with the line H1 connected to the magnet 25 of each module and with the remaining lines similarly connected to the other electromagnets. The sequence controller also has four sets of output lines V1-V4, with the set V1 connected to the stepping motor 21 of each module and with the remaining sets similarly connected to the other motors. The sequence controller is actuated by the symbol identification portion of the incoming data and applies an output voltage to the H output line corresponding to the parti-cular piece of data to be changed. For the stock price example, a new high price would call for output voltage on line H3 which would tend to actuate the corresponding row selector lever of each module. Since the relay 16 is actuated in only one module, only the row selector lever on the one module will be moved. The sequence controller then applies stepping voltages to the output sets V1-V4 to rotate the shafts to move the appropriate symbols into position for viewing. The present application is directed to a new stepping motor drive for use in the sequence controller and this drive system is shown in FIG. 4;

Referring to FIG. 4, the incoming message in a multibit digitial code form enters an eighteen-bit shift register 40. Various portions of the message are selected from the register for various uses in connection with the display board, including actuation of module relays, actuation of horizontal lifter magnets, and actuation of the stepping motors for the vertical shafts. In the present application,

we are concerned with the stepping motor operation. The

timing of the input message provides the timing control for the controller with the message input being connected to a clock pulse source 41 which provides a pulse train output as indicated at 42. The clock pulse train 42 provides an input to a gated binary counter 43 which runs when ungated to count clock pulses and provide an output having a polarity change for each clock pulse, as indicated at 44. The counter 43 is controlled by gates G1 and G2 and runs when G1 is reset or off and G2 is set or on. The output 44 of the binary counter 43 provides the shifting pulses for a multistage reversible shift register comprising flip-flops 45, 46, 47. The output ofthe shift register is inverted with respect to the input, as indicated by the conductor 48 connecting an output of the Hip-Hop 47 to an input of the flip-flop 45 and the conductor 49 connecting an output of the fiip-op 47 to an input of the dip-flop 45. The shift register is reversible as indicated by the arrowheads at both ends of the conductors interconnecting the inputs and outputs. Each flip-flop of the shift register corresponds to a coil of the stepping motor to be driven, the flip-flops being identified as M1-|-, M3-, and M2|-. The symbol M1-lindicates that when the fiip-iiopv45 is in the set condition, the polarity of the voltage at the M1 terminal 13 is positive. Similarly, when fiip-op 46 is in the set condition, the voltage at terminal M3 is negative and when flip-flop 47 is in the set condition the voltage at terminal M2 is positive. l

Shifting of the register produces a corresponding stepping of the motor, as will be described hereinbelow, with shifting in the direction which produces clockwise motor rotation being referred to as clockwise shifting and shifting in the direction which produces counterclockwise motor rotation being referred to as counterclockwise shifting.

The direction of shifting is controlled by a selector switch 52 which produces a pulse train output from the counter output 44 and selectively couples this pulse train output to a counterclockwise shift line 53 or to a clockwise shift line 54.

Thek output from the nip-flop 45 provides the vcontrol for a three-position switch 60. Similarly, the outputs of flip-flops 46 and 47 provide the control for switches 61 and 62. The switch 60 has two inputs, a positive voltage source on line 63 and a negative voltage source on line 64, and a single output on line 65 which is connected to the M1 terminal 13 of the stepping motor. When the flip-Hop '45 is switched to the setcondition, the switch 60 is switched tothe positive condition to connect the source 63 to the line 65. When the flip-Hop 45 is switched to the reset condition, the switch 60 is switched to the negative condition to connect the negative voltage-on input 64 to the line 65. The switch 60 may be moved to the off position connecting neither voltage source to the stepping motor coil after being moved to the positive or negative position, by an intermediate switching means incorporating the motor off logic unit 66.

As indicated previously, the selector switch -52 provides y'a shift pulse output for every other voltage change in the input 44. The intermediate voltage changes in the signal 44 provide the timing for the motor off-logic to switch one ofthe three-position switches to the olf condition intermediate each shifting step of the shift register.

The numbers for the cylinders of the display module and hence for the angular positions of the stepping motor are identified by a four-bit binary code as follows:

The binary code for a number in each of the hundreds, tens, ones and eighths columns of a moduleiscontained in a single message format, as shown in FIG. 5. The timing logic unit .67 provides for extracting the bits of a number code from the message in the manner shown in the timing diagram of FIG. 6. ,The first -bit of the fourbit number code serves to set the selector switch 52 with the switch being set for clockwise shifting pulses for a one `and counterclockwise shifting pulses for a zero. The shift register is not advanced by the first bit of the four-bit number code but the direction of rotation of the stepping motor is selected. If the second ybit of the four-bit number code is a one, the counter 43 is ungated to run a predetermined length of time to'produce a predetermined number of shift pulses for the register. Similarly, if the third bit is a one, the counter is ungated to produce another number of shift pulses and if the fourth bit is a one, the counter is ungated to produce another number of shift pulses.

The sequence of operation is as follows. The counter runs when G1 is reset and G2 is set. G1 is set by the sixth character-first bit and is reset when G2 sets. G2 is reset at the sixth character-sixth bit, -a the seventh characterfourth bit, and at the first character-second bit, for the second, third and fourth 'bits of the four-bit number, respectively. G2 is set on the sixth character-first bit if the second bit of thefour-bit character is a one, is set on the seventh character-first `bit if the third bit of the fou-r-bit Word is a one, and is set at the first character-first bit if the fourth -bit of the four-bit word is a one. By this means, the number of shifts produced in the shift register and hence the number of steps produced in the motor is controlled by letting the counter run for predetermined number of counts, depending upon the presence or absence of ones in the second, thi-rd and fourth bits of the four-bit number code.

After the stepping motor has been stepped an appropriate number of times to drive the cylinder to the desired position and after the cylinder' has been disengaged from the motor shaft, the Amotor isreturned to the home position to await another input signal. This is accomplished 'by ungating the binaryy counter 43, permitting the register to shift and the motor to step until the motor is in the home position. The direction required for stepping the motor homev through the smallest angle is4 determinedl by sampling the output from the flip-op 45 via a direction to home unit 70. If the M1+ output lead lof ip-op 45 has `a positive voltage thereon, stepping in a counterclockwise direction iwill bring the motor home in the fewest number of steps and hence the direction to homev unit 70 actuates the selector switch 52 to provide counterclockwise shift pulses. Similarly, if the Ml-llead has a negativevoltage thereon, clockwise shifting pulses are called for.

The outputs from the three ip-ops `are connected to the homing logic unit 71 as inputs `with the homing logic unit providing a set signal on line 72 to G2 if the three ip-ops are not in the home condition. This set signal ungates the counter 43 producing shifting of the register. When the motor has stepped to the position next to home, a reset signal is generated on the line 73 for resetting G2 `and shutting off the counter after one more step has occurred.

In the embodiment described herein, the input message is a one hundred word per minute signal similar to a standard teletype signal. A se-ven-character message is required to set one display module, the message format being shown in FIG. 5. The number code bits for Ia given number do not come all in one character but are received one at a time in different characters and the number codes are defined in such a way to provide automatic stepping of the motor to the correct number position.

For example, in setting the number 0 (1111 code), the first `bit of the four-bit code is received lwith one of tht rst four words of the message providing a 1000 code which acts to-select the direction of rotation. The next bit is received with the 4fifth character of the message making the code 1100 which is the code for the number 4 `and the motor is stepped to the 4 posit-ion. With the sixth character another bit is received making the code 1110, setting the motor to the 8 position. Finally, the last bit is received with the seventh character giving a 1111 code which lsends the motor to the 0 position.

The motor is sequencedA automatically in step -with the shift register with the stepping occurring as the four-bit number code is filled out one bit at a time. If the number to be set has been an 8, the final bit received with the seventh character would have been a 0 leaving the vcode unchanged at 1110 and leaving the motor set .at 8.

The control circuitry keeps track of lwhat character of the message is being received `with a seven state counter in the timing logic, which counter is reset whenever a synchronizing code is received. Synchronizing codes (111111) are set whenever the line is not busy. Since thecharacter counter is held in the word one 4state whenever synchronizing codes are received, the character counter starts counting vas soon as the sending'of the information is resumed.

Referring to the message-format of FIG. 5, it is seen that at the end of the third character the three letters of the stock symbol are available. These are decoded by a separate mechanism to yactuate a particular module relay to complete the ground return circuits in the selected module. The fourth character of the message provides the information for selectively energizing a horivzontal lifter electromagnet, engaging the cylinders of the module in the desired horizontal row. The fifth, sixth and seventh characters of the message provide the number code bits for setting and resetting gates G1 and G2 to control the running of the binary counter. Bit 5 of the fifth, sixth and seventh characters provides additional information which may be substituted for the information of one of bits 1-4 or used separately or discarded, as desired.

As indicated previously, with the three flip-flops 45, 46, 47 of the shift register identified as M1+, M3 and M2+, respectively, the states of the flip-ops correspond to the stepping motor coil'polarities as shown in FIG. 3 for sequencing of the motor. A one in the Ml-lflipflop means .that the M1 motor coil 10 has a positive voltage connected thereto while a ze-ro means that ya negative voltage is connected thereto. The right or clockwise shift counting sequence for the register is as follows:

Flip-Flop States Coil Polarities Motor Position Mr-l- M3- Mz-i- M! M2 M;

1 ,0 0 -l- -l- X 1 1 1 -l- 2 1 1 1 -l- -l- 4 c 1 l -l- 6 0 0 l -l- -l- 8 0 0 0 -l- O(Y) The counting sequence for the left ,or counterclockwise shift is as follows:

' -The intermediate steps between the number positions of FIG. 3 with zero motor current on one coil are produced by the motor off logic switching circuit 66. The shift register is advanced for every other pulse in the clock pulse train 42 so that the motor is advanced one position for each pulse when the binary counter 43 is running. The number of steps from home produced in the motor is determined by the number code lreceived in the message, the number code for each position of `the motor being shown in parentheses -in FIG. V3. The first bit of the number code determines Whether the register and hence the motor shall go clockwise or counterclockwise. The .remaining three bits lof the four-bit number code are assigned a weight 6-4-2, respectively, and produce a number of pulses equal to one more than the number of steps required for display. The rst pulse is discarded in the resetting of G1 and setting of G2. For example, the four-bit code for the number 6 is 1101 which means thefmotor lwill step clockwise (6-1)+0+2=7 steps from home to position the motor at 6 for displaying the numeral 6 on the cylinder.v Similarly, 0 having a code 1111 calls for yclockwise stepping (61){-4|2=11 steps from home. The c-ode for 1 is O01()v calling for counterclockwise 0+(4-1) +0=3 steps from home. i

The binary counter 43 is ungated by the action of the gates G1 and G2 as previously described with the timing being'shown on FIG. 6. The pulse train 42 corresponds to the bit or T counter transitions, there being six bits per character as seen in FIGS. and 6. The gate G2 gets reset pulses on the sixth shift pulse of'fthe sixth character, the fourth shift pulse of the seventh character and the second shift pulse of the first character. The gate is turned on or set at the beginning of the sixth, seventh and rst characters only if the number code bits two, three or four are one, permitting six, four or two pulses to be ungated into the counter. The-gate G1 is set at the beginning of the sixth character and is reset on the rst pulse received after the gate G2 sets. Since the counter does not count unless G2 is set and G1 is reset,'one pulse is subtracted off, resulting in the desired number of motor steps.

The three-position switch 60 may take any conventional form and preferably comprises a pair of electronic switches, one providing for connecting the positive supply to the motor coil and the other for connecting the negative supple to the motor coil. The turning off of a motor coil at the intermediate step is produced by the motor off logic unit 66.y The logical equations .for plus, minus and zero outputs on the motor coils are as follows:

*Md means either Mi+ Aflip-flop 1s true or iNIifllp-flop is false, whichever is applicable. subtract 3. MP means motor power. b is the output of the counter 43 and goesfalse on the intermediate pulse from the counter.

In anlalternative form of the invention, the intermediate steps and the motor off logic may be omitted with the stepping motor having only six positions. In this embodiment, `the shift register can be arranged to shift with every count of the counter with the counter being gated to provide three, two and one counts for the second, third and fourth bits of the four-bit word, or the register can be operated to shift with every other count in the manner previously described. Of course, the count condition of the register and the position of the stepping motor and hence the number displayed on the cylinder must be properly correlated. The intermediate stepping operation described in the first embodiment is preferred as it provides a smoother operation. Also, the intermediate stepping operation permits the positioning of the motor at twice the number of positions, although only six positions are presently being used in the display board.

Although exemplary embodiments of the invention have been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiments disclosed may be subjected to various changes, modifications and, substitutions without necessarily departing from the spirit of the invention.

We claim as our invention:

1. In an open loop controller for ya stepping motor having a plurality of `drive coils positioning a rotating member as a function of the excitation of the coils with the controller driving the rotating member in a selected direction to a selected position, -the combination of:

av multistage reversible shift register with the output inverted to the input and having a stage corresponding to each drive coil;

means for selectively shifting said register a predetermined number of counts clockwise and counterclockwise in response to an input code;

a power switching unit for each drive coil and including means for selectively energizing the drive coil in opposing polarities from a power source; and circuit means for coupling the output of a shift register stage to a corresponding power switching unit in controlling relation for energizing a drive coil as a function of the corresponding register stage condition. 2. In an open loop controller for a stepping motor having nfdrive coils positioning arotating member as a functionof the excitation of the coils with the controller driving the rotating member in a selected direction toV a selected one of 4n positions, the combination of:

an n stage reversible shift register with the output inverted to the input and having a stage corresponding to each drive coil; l v means for selectively shifting said register a predetermined number of counts clockwise and counterclockwise in response to an input code; a power switching unit for each drive coil and including means for Vselectively energizing the drive coil in opp posingpolarities from a power source;

circuit means for coupling the output of a shift register stage to a corresponding power switching unit in controlling relation for energizing a drive coil as a function ofthe corresponding'register stage condition; and intermediate switching means coupled to eachof said power switching units in controlling relation for de- If +12 is greaterthan 3,-

-energizing a drive coil at a time intermediate the shifting times of said register.

3. In an open loop controller for a stepping motor having a plurality of drive coils positioning a rotating member as a function of the excitation of the coils with the controller driving the rotating member in a selected direction to a selected position, the combination of:

a multistage reversible shift register with the output inverted to the input and having a stage corresponding toA each drive coil;

means for selectively shifting said register a predetermined number of counts clockwise and counterclockwise in response to an input code and including means for generating a shift pulse only for alternate pulses of a timing pulse train;

a power switching unit for each drive coil and including means for selectively energizing the drive coil in opposing polarities from a power source;

circuit means for coupling the output of a shift register stage to a corresponding power switching unit in controlling relation for energizing a drive coil as a function of the corresponding register stage condition; and

intermediate switching means coupled to each of said power switching units in controlling relation for sequentially de-energizing a drive coil in response to the intermediate pulses of the timing pulse train.

4. In an open loop controller for driving a stepping motor in response to a multibit digital code, the motor having a plurality of drive coils positioning a rotating member as a function of the excitation of the coils with the controller driving the rotating member in a selected direction to a selected position determined by the input code, the combination of:

a multistage reversible shift register with the output inverted to the input and having a stage corresponding to each drive coil;

means for generating clockwise and counterclockwise shifting pulses for said register including means for selectively coupling said clockwise and counterclockwise pulses to said register as a function of the first bit of the input code for determining the direction of shift of said register;

means for controlling the number of shifting pulses coupled to said register as a function of the succeeding bits of the input code for shifting said register in a predetermined direction to a predetermined condition;

a power switching unit for each drive coil and including means for selectively energizing the drive coil in opposing polarities from a power source; and

circuit mean-s for coupling the output of a shift register stage to a corresponding power switching unit in controlling relation for energizing a drive coil as a function of the corresponding register stage condition.

5. In an open loop controller for driving a stepping motor in response to a multibit digital code, the motor having a plurality of drive coils positioning a rotating member as a function of the excitation of the coils with the controller driving the rotating member in a selected direction to a selected position determined by the input code, the combination of:

a multistage reversible shift register with the output inverted to the input and having a stage correspondto each drive coil;

means for generating clockwise and counterclockwise shifting pulses for said register including means for selectively coupling said clockwise and counterclockwise pulses to said register as a function of the first bit of the input code for determining theidirection of shift of said register;

a timing pulse train source;

gate means for coupling said pulse train source to said means for generating for periods determined by each of ther succeeding bits of the input code for shifting said register in a predetermined direction to a predetermined condition;

a power switching unit for each drive coil and including means for selectively energizing the drive coil in opposing polarities from a power source; and

circuit means for coupling the output of a shift register -stage to a corresponding power switching unit in controlling relation for energizing a drive coil as a function of the register stage condition.

6, In an open loop controller for driving a stepping motor in response -to a four-bit digital code, the motor having three drive coils positioning a rotating member as a function of the excitation of the coils with the controller driving the rotating member in a selected direction to a selected position determined by the input code, the combination of a three-stage reversible shift register with the output inverted to the input and having a stage corresponding to each `drive coil;

means for generating clockwise and counterclockwise shifting pulses for said register including means for selectively coupling said clockwise and counterclockwise pulses to said register as a function of the first bit of the input code for determining the direction of shift of said register;

a timing pulse train source;

gate means for coupling said pulse train source to said means for generating for periods determined by each of the succeeding bits of the input code for shifting said register in a predetermined direction to a predetermined condition with the second, third and fourth bits having the ratio 3:2zl;

a power switching unit for each drive coil and including means for selectively energizing the drive coil in opposing polarities from a power source; and

circuit means for coupling the output of a shift register stage to a corresponding power switching unit in controlling relation for energizing a drive coil as a function of the register stage condition.

7. In an lopen loop controller for driving a stepping motor in response to a four-bit digital code, the motor having three drive coils positioning a rotating member as a function of the excitation of the coils with the con- -troller driving the rotating member in a selected direction to a selected position determined by the input code, the combination of:

a three-stage reversible shift register with the output inverted to the input and having a stage corresponding to each `drive coil;

means for generating clockwise and counterclockwise shifting pulses for said register including means for selectively coupling said clockwise and counterclockwise pulses to said register as a function `of the rst bit of the input code for determining the direction of shift of said register;

a timing pulse train source;

gate means for coupling said pulse train source to said means for generating for periods determined by each of the succeeding bits of the input code for shifting said register in a predetermined direction to a predetermined condition with the second, third and fourth bits having the ratio 3:2:l;

a power switching unit for each drive coil and including means for selectively energizing the drive coil in opposing polarities from a power source;

circuit means for coupling the output of a shift register stage to a corresponding power switchingunit in controlling relation for energizing a drive coil as a function of the register stage condition; and

intermediate switching means coupled to each of said power switching units in controlling relation for deenergizing a drive coil at a time intermediate the shifting times of said register.

(Other references on following page) 1 1 1 2 References Cited By the Examiner 3,176,208 3/ 1965 Gt 318-28 3,178,624 4/1965 Borden 318-138 X UNITED STATES PATENTS 3,218,535 11/ 1965 Holthaus et a1 310-49 X 2,537,427 1/1951 Se1d et al. 318-28 v 3,124,732 3/1964 Dupy 31g 138 5 GRIS L. RADER, Prlmary Examlner. 3,127,548 3/1964 Van Emden 310--49 X G. SIMMONS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3, 297 ,927 January 10, 1967 Thomas R. Blakeslee et al It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l, line 33, second occurrence, strike out "at" column 5, line 55, for "a" read at -l; column 6, line 45, for "has" read had line 52, for "set" read sent column 7, in the first table, third column, line 2 thereof, for "1" read D same table sixth columnJ line 4 thereof, for read same column 7, second table, third column, line 2 thereof, for "O" read l Signed and sealed this 17th day of October 1967.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. IN AN OPEN LOOP CONTROLLER FOR A STEPPING MOTOR HAVING A PLURALITY OF DRIVE COILS POSITIONING A ROTATING MEMBER AS A FUNCTION OF THE EXCITATION OF THE COILS WITH THE CONTROLLER DRIVING THE ROTATING MEMBER IN A SELECTED DIRECTION TO A SELECTED POSITION, THE COMBINATION OF: A MULTISTAGE REVERSIBLE SHIFT REGISTER WITH THE OUTPUT INVERTED TO THE INPUT AND HAVING A STAGE CORRESPONDING TO EACH DRIVE COIL; MEANS FOR SELECTIVELY SHIFTING SAID REGISTER A PREDETERMINED NUMBER OF COUNTS CLOCKWISE AND COUNTERCLOCKWISE IN RESPONSE TO AN INPUT CODE; A POWER SWITCHING UNIT FOR EACH DRIVE COIL AND INCLUDING MEANS FOR SELECTIVELY ENERGIZING THE DRIVE COIL IN OPPOSING POLARITIES FROM A POWER SOURCE; AND CIRCUIT MEANS FOR COUPLING THE OUTPUT OF A SHIFT REGISTER STAGE TO A CORRESPONDING POWER SWITCHING UNIT IN CONTROLLING RELATION FOR ENERGIZING A DRIVE COIL AS A FUNCTION OF THE CORRESPONDING REGISTER STAGE CONDITION. 